Buffer spring assembly for automatic firearms



April 25, 1950 RE. BOTTS ETAI- BUFFER SPRING ASSEMBLY FOR AUTOMATIC FIREARMS 3 Sheets-Sheet 1 Filed Jan. 31, 1946 Enhrt '.E! at :5 Limit F-Yuun wiimo April 25, 1950 -rs ET AL I 2,504,958

BUFFER SPRING ASSEMBLY FOR AUTOMATIC FIREARMS Filed, Jan. 31, 1946 3 Sheets-Sheet 2 Robert IlEutts Lautt RYuung 3% a. amp/arm) April 25, 1950 T-rs EIAL I 2,504,958

BUFFER SPRING ASSEMBLY FOR AUTOMATIC FIREARMS Filed Jan. 31, 1946 '3 Sheets-Sheet 3 EHQIIL 47 56 jwum vbow Robert E. Emits Lauii PM cxmw mmw I Patented Apr. 25, 1950 BUFFER SPRING ASSEMBLY FOR AUTOMATIC FIREARMS Robert E. Botts, Blue Earth, Minn, and Lautt F. Young, Chafiee, Mo.

Application January. 31, 1946, Serial No. 644,646

(Granted under the act of March 3. 1883, as amended April 30, 1928; 370 O. G. 757) 2 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to us of any royalty thereon.

The invention relates to bufier devices for reciprocating elements of automatic weapons and particularly is applied to means for stoppin and returning the barrel and barrel extension of the recently standard Browning machine gun which has been largely produced in caliber .50 size. There, an oil bufier device has been used in conjunction with a spring performing the counterrecoil movement. This prior practice is illus-- trated in the patent to Browning, No. 1,628,226. The invention is also applicable to guns of other caliber using similar actions, and may be adapted to arms using other actions. It is an important aim, attained by the invention, to improve the functions of the gun action to the extent of eliminating bucking, heretofore experienced in the operation of such guns, which has greatly interiered with aiming of the weapons, and has prevented trackers from changin the target or maintaining a line of sight on a single target, at reasonable ranges. In other words, the invention seeks to attain a smooth rapid fire operation of such weapons, which in practice with the instant embodiment has enabled performance by a .50 caliber gun in a manner which corresponds to the best operation of much smaller caliber rapid fire guns.

Attending the last mentioned improvement is an increase in effectiveness of tracking in antiaircraft fire; attainment of a more concentrated bullet pattern (disregarding effects of irregularities in ammunition); maintenance of a constant value bullet pattern (whereas the prior oil buffer would vary from time to time by changes of temperature, lack of prompt and frequent servicing and adjustment, or delay in replenishment of oil; and by failure of the device to retain adjustments when once made), and reduction of climbing. The effects of depletion of oil may be understood from the fact that an oil buffer two-thirds full suffers a pattern drop of four inches. A further important object of the invention is to minimize the necessity for changin current and past production forms of essential parts of the loading and firing mechanisms heretofore used in order to apply my invention 1 A further desideratum is to retain the essen tial advantages of the prior construction, such as adjustability to coordinate the bufier with the rate of fire and to enable adjustment of the rate of fire and counterrecoil timing. A further important aim is to simplify the servicing and maintenance of the weapon, particularly with respect to need for special material and freedom from likelihood of impairment by dust and dirt which is a constant accompaniment of field warfare. It is also a purpose to reduce drastically the number of parts and the complexity of the manufacture of those remaining at the same time that the foregoing advantages are attained,

It is also an important object to pres nt a mechanism liable in minimum degree to malfunc tions attributable to the buffer device. It is also an aim to eliminate requirement of special knowledge and service facilities or practices in maintenance of the buffer, and to reduce to an extreme the need of replacement, adjustment or repair. It is especially sought to enable the use of a spring buffer which may be assembled in the oil buffer tube and body as heretofore manufactured, and so coordinated therewith that adjustments for rate of fire and smoothin operation may be made by the same parts and tools heretofore used for those purposes in the oil buffer device. This will enable conversion of present weapons by discarding parts and substitution of fewer and simpler parts. Also to present a markedly simplified device of the improved nature which may be used in the buffer mounting as a substitute for the whole oil buffer assembly.

A salient motive in the invention is to produce a rugged device which the ordinary gunner can readily understand without exceptional knowledge or training and which may more readily to be taken apart and be assembled in the field without disturbance or impairment of function.

Other objects, advantages, and features of the invention reside in the construction, arrangement, and combination of partslnvolved in the embodiment of the invention, as will be understood from the following description of accompanying drawings, wherein:

Figure 1 is a longitudinal section of a buffer assembly installed in a current production model of .50 caliber Browning machine gun, utilizing the prior oil buffer spring and tube, the gun being in battery;

Figure 2 is an exploded View of the Old 011 tube and new parts of the device of Figure I;

Figure .6 .is a section of a modification in which the oil bufier tube and other parts are omitted but utilizing the prior oil buffer body and other parts of the action without change,

Figure '7 is a, cross section on the line Fl-4| of Figure 6.

Figure 8 is a cross section on the .line 13-18 of Figure 6.

Figure 9 is a section on ure 6.

Figure 10 is an elevation of a preferred embodiment of the invention representing a complete buffer unit adapted to be set in place in a standard buffer body ,LU hereinafter described, as a replacement of prior oil buffer devices; "Figure '11 is a "longitudinal section of Fi ure10;

Figure 12 is a s'imflar view with the buifer compressed;

Figure 13 is 2, cross section on the line 13-43 of Figure 11;

Fig-ure 14 is a section on the line -14 of'Figure ll';

"Figure 15 is a section on the line -ll-5 of Figure 11.

"Uonsidering the drawings, there is illustrated in Figures 1 to 5a buffer assembly which is adapted to beset in the heretofore familiar oil buffer body orcase I 0 which =now,withoutchange, functions simply as amounting or carrier and guide body. Thisbody, as heretofore well-known; ismountable fixedly the receiver 1-! of a gun largely in use, wherein it rests against the back plate 1 2. We also use, without change, the .oil

the .line ,9-9 of Figbuffer tube as a spring case l3 :revoluble as Eheretofore, inthe body. This tub isformed with longitudinal grooves andribs ofserratedform whereby it may be secured by a spring lock or latch 44 against casual rotation in the body I10, but remains elidable therein and yieldable to manual rotation by .a screw driver inserted through :an aperture [:5 in the back plate. The rear end of this tube also bears against the back plate :12 of the receiver. A cap !6 screwed into the forward end of thetube may also be the same as heretofore used in the oil-buffer but requires no packing devices. A plunger rod :11 is engaged loosely and slidably -through this camp, similar to the prior piston rod used the oil buffer except that it is slightly shorter. It is threaded for a goodl distance on its rear end and screwed into an interiorly threaded presser head It which fits the interior of the tube slidably and has .one or more spline keys 1,9 to lit the interior longitudinal grooves 18 customarily formed in the wall of the tube. Confined between thehead l8 and the rear closed end of the tube there is ahelical wire buffer rear spring 20 of such length that it is quite unloaded when the head it is at the forward limit of itsmovement in the tube lS-close .to the cap 15. Its load-depression characteristic may be calculated in accordance with the extent of recoil of the barrel, which it is desired that this spring shall neutralize in conjunction with the function of a forward buffer spring 2|, which sustains the entire recoil movement, but only art of the load, and may be the same as the regular oil buffer springheretofore used. 'I'helatter spring is confined between the cap 16 and a spring seat and guide collar 22 which is the same as heretofore used in the oil buffer and likewise pinned at 23 to a plunger head 24 which has the forwardly projected jaw 25 the same as the head of the piston rod of the oil buffer heretofore. It is shaped .to interlock with the barrel extension shank 25 ao'f the barrel extension in the familiar gun action as before. The collar 22 has at least one key 2'! :sl'idable in a corresponding slot heretofore provided in the body mount l0.

in the use of "the invention in the form thus disclosedyth'e gun functions with the same sequence of movements and closely similar functions as bezfore, but with certain distinctions and with new results in the absence of irregularity of t1 8 delay function and recoil absorption quality, as well as contributing to counter-recoil movement and a capability of controlling firing rate over a greater range. "-It has been found practicable to operate the gun so equipped at a much higher rate of fire than can be maintained with the oil buffer. Adjustment of the rate is obtained rotating the tube 13 by means of a tool'inserted through the aperture 15 in the back plate to engage the-end of the tube as before indicated. In such rotation, the ipress'er liead' being keyed to the tube and the collar 22 keyed to the body and pinned to the plunger, the presser head I8 is caused to rotate on the rod and draw itself forwardly or rearwardly, according to the direction of the rotation of thesleevethereby varying the degree of the dep'ression of the rear spring 2!) when the barrel recoils and so controlling the cushioning effect and rate of fire, as is well understood in the adjustment of these actions.

lt should be appreciated that it is not necessary nor intended that the two springs described shall absorb and counteract the entire energy of the recoil of the barrel, but there is a certain remainder of velocity of recoil manifest after the entire deceleration resulting from action of the springs so that the recoil may be finally stopped by engagement of the barrel extension against the buffer body case II! as heretofore.

In Figures 6 to 9 a modification of the construction is shown in which further simplification and reduction of cost is attained, retaining .the advantages of function and. improvement before enumerated.

Here, a new tube .or sleeve 30 of smaller diameter than the tube I3 is substituted for the tube I3 and in place of the small rod l1, cap 16, and pressure head IS, a one-piece plunger rod 3| of round stock is provided, fitted slidably in the tube 30, its forward end being shaped to provide the jaw 25' of the same shape and dimensions as the jaw 25 before described. The rear end of the sleeve 30 is closed by a screw plug and spring seat 32, and the rear end of the plunger at an initial position stops short of the plug sufficiently to accommodate a rear or bumper spring 33 corresponding to the one '20 and also clears the sleeve somewhat, so that the free spring 33 sets in the tube with a length substantially less than the distance from the plunger to the'plug when the plunger is at its forward limit of movement. This limit, which marks the normal initial position of the plunger, is determined by a cross pin 34 engaged through the rear extremity of the plunger, projecting at each end into longitudinal slots 35 in the tube 30. The pin engages the forward ends of the slots when the plunger is at the forward limit of its movement, but stops short of the rear ends of the slots when the plunger moves to the rear limit of its movement. This rear limit is reached when the barrel extension of the gun action engages the forward end of the buifer body or case ill.

The forward end 36 of the plunger is of approximately the same diameter as the head 24 and has a guide collar 22 pinned thereto which may have the same initial position as in the first described device and as in the oil bufier. The main buffer spring 31 in this device, corresponding to the forward spring 2| of Figure 1, is much longer than the spring 2| and is engaged exteriorly and loosely around the tube and loosely within the body or case it. The rear end of the tube 30 has a foot flange 38, smoothly finished on its periphery and set against the back plate of the receiver, fitting the case In slidably and revolubly when being assembled but being fixed against rotation after assembly by means of the cross pin 34, and engagement of the key 21 in the case ID. The spring 31 is seated upon the flange 38 and is confined by the sleeve 30 and spring seat 22 in the same manner in which the spring 2| was held. The spring 31 may be made of somewhat heavier wire stock than the former oil buffer spring, the diameter of the stock in one embodiment having been 0.125 inch, its free length seven inches, with 14 turns, and its outside diameter 1.350 inches. The spring 33 has been made from a similar stock with eight turns, outside diameter of 0.770 inch, and a free length of 1.125 inches, but a lighter stock may be employed with more turns in this spring. The eifect of the spring 33 may be regulated by adjustment of the screw plug 32 rotatively to vary the degree of depression of the spring by the plunger incident to recoil of the standard barrel and barrel extension of the gun as heretofore constructed. This has itseffect on the rate of fire and on the smoothness of operation, or stability, of the gun in action. In connection with the rate of fire it may be explained that the action in the specific gun mentioned is such that. the bolt and firing device are keyed with the barrel and barrel extension during the last increment of counterrecoil movement of the bolt so that adjustment of the spring 33, to hasten counter recoil of the barrel and barrel extension, accelerates action of the bolt and firing device.

The advantages of the present invention over the oil or air dashlpot device (the oil buifer being essentially a dashpot device), lies partly in the fact that in the dashpot device entire inertia of the barrel and barrel extension after recoil must be overcome, and counter recoil movement ef fected, by the single spring such as the oil buifer spring, which is not an eflicient one for the initiation of such movement, whereas the more resistant springs 33 and 2|), here shown, are hi hly effective in such initial work, while the springs 31 and 2! are amply effective for further acceleration of the necessary parts in the final counter recoil function. There is also a function in smoothing the operation of the gun consisting in the possibility of adjusting the period reaction of the second spring (2!) or 33) to, coincide with recoil movements and/or counter recoil movements, so that vibrations which the operation of the mechanism tend to set up are counteracted by tim d or proportioned react on of the buffer or bumper -springs, and by interference of opposing vibrat on sources a stabilization of the piece during rhythmic rapid fire is attained.

There is illustrated in Figures 10 to 15 inclusive, a preferred embodiment of the invention in which the part 40 corresponding to the tube or sleeve 30 and tube I3, is in this instance also of such proportions that it may be set in the case [0, although it may be otherwise constructed for other breech mechanisms.

The tube 40 is a simple casting or forging having a rear cylindrical thick walled body 4| formed with a reduced forward concentric extension 42' the base of which is slightly enlarged. A main spring seat 43 is constituted around this base by the larger body portion of this piece. The pieceis bored as at 44 from end to end with a uniform diametertlfirteen-sixteenths inch in this example-and interiorly threaded at the rear end only. The forward part of the body is formed with two diametrically opposed radial guide slots 45, extending from the bore through the outer face of the body. These slots extend longitudinally from near the seat 43 to within a suitable distance of the rear end face of the tube, and receive therein short guide pins or studs 46 set diametrically in the sides of a piston plunger 41 consisting of simple round stock fitted slidingly in the bore 44 and having at its forward extremity the jaw 25 as before described. It has the collar 22 held thereon as before. The pins 46 limit forward movement of the piston 41 so that the jaw 25 is properly spaced from the back face of the tube 40 for interlock with the barrel extension of the weapon in which it is to be used, as before explained; and when so engaged the seat 43 is spaced properly from the collar 22 to allow the main spring 48 to be confined between the two. This s ring has a helical winding of one-eighth inch diameter standard round stock steel spring wire, with ten coils, wound to an inside diameter of 1.1875 inches. Its free length in such example is five and a quarter inches and in assembly at normal initial extended positions of the buffer parts, it extends over approximately two and three quarter inches.

In the rear threaded end of the bore in the body 4|, there is engaged an adjusting screw 49 entirely within the body AI and having a cylindrical seat post 56 half an inch in diameter formed coaxially therewith of substantially less diameter than the bore 41, and the piston 41 is bored from its rear end to a diameter to receive the post 59 freely and slidably therein. A cylinder or spring chamber 5! is thus formed. The

latter extends forwardly considerably more than the full stroke of the piston as will be more definitely disclosed hereinafter. A seat 52 is thus aiforded on the screw around the base of the post 5!). In the space within the bore as around the post 50 there is set a second helical spring 53, which is also of one-eighth inch wire with six full coils Wound to an inside diameter of slightly more than half an inch (.53 inch) so as to fit loosely around the post 50 and clear of the sides of the bore 44. It has a free length of one and nine-sixteenths inches while the longitudinal clearance between the seat 52 and the end M of the piston is approximately two and one-eighth inches when the gun is in battery and the piston at its forwardmost position in the tube 40. In consequence, this spring is initially free of load and lies loose in the bore 4 1 with an end clearance in the bore of approximately one half inch.

The post as is of sufiicient length to extend a short distance into the chamber 5! when the piston is at its forward limit, and the chamber extends further forwardly therefrom approximately two and nve-sixteenths inches. A third helical Wire spring '55 is laid in the chamber This, for example, has been made of .071 inch diameter round wire spring stock, the helix having an inside diameter of .338 inch and seven coils, and a free length of one and one-sixteenth inches. The post 56 is of such length that the longitudinal clearance in the chamber 5| between the spring 55 and the ends of the chamber when the piston is at its forward position is slightly less than the total desired travel of the piston, which is the same as the travel of the barrel extension in the gun action, or, for this examplefon'e and one-eighth inches.

'It is intended that in the last described form of the device on firing of the weapon there will be a progressive compression of the main spring 48 throughout the rearward movement of the piston and it is also intended that the stresses developed in this spring by the full travel of the piston shall be much less than required to stop the piston and connected recoiling parts. Also it is intended that the full travel of the piston will also be less than required to compress the spring to solid position. In consequence, a spring may be used which is comparatively flexible and which will be subjected to stresses far from critical as the full stroke recoil position of the piston. Thus, liability of its breakage is greatly reduced and shock tending to fracture it by abrupt compression eliminated.

The second spring is likewise intended to have a similar relation to the movement of the piston when the later has begun compression thereof after a certain degree of movement of the piston inch more or less, for instance) without impedance by this spring. The permission of this early movement of the piston clear of this spring enables the use of a comparatively stifi spring here for the further retardance of the piston Without requiring the spring to function through a great extent of movement, so that the point of stoppage of the piston in engagement with this spring will also be far short of the springs solid position, and also far short of its critical depression. It is further the purpose to so proportion and temper these two springs that their aggregate force of reaction exerted at the moment of stoppage of the piston will be less than that which is required to stop the piston and the connected recoiling parts. This aggregate force may be approximately 75% of the force required to stop the recoiling parts and of this the main spring may exert 45% and the second spring 30%. The third spring has somewhat similar relation to the degree of depression thereof by the piston while engaged therewith in movement to stopped position, and is only slightly depressed when the movement of the piston ceases. Thus it also is subject to immaterial shock, and its fiexure stops far short 'of critical stress therein. The component of reaction force supplied by this spring opposing recoil movement of the piston is less than that required to stop the piston when added to the sum of force exerted by the first two at the stopped position of the piston. This third spring may supply in the neighborhood of twenty percent {20%) of the force required to stop the piston. These components may not be the exact ones derived from the respective springs but are stated to indicate the general relation between the three springs and recoil parts. It will be noted that the sum of the forces stated is less than required to stop the recoil at the desired 8, limit, and this is supposed, because a, certain unbalanced force of'irioinentiim is intended to be manifest to be absorbed by a bufi'e'r body case back plate and the disc assembly 56, shown in Fig. 1 as heretofore familiar.

The exact remainderto-be absorbed bythe discs may be more or less than specifically indicated by the components named, but may be in pro; portion to that involved in the ideal operation of prior bufier devices of this general kind. The ratio of the remainder to the whole stopping force required may be varied by adjustment of the screw 49 which is .provided; with atransversely slidable spring-pressed latch pin 51, the rounded head of which is exposed at one side of the screw to engage in diametrically opposite longitudinal channels 6B in the sides of the bore 44, yieldable to rotation of the screw by an instrument such as a screw driver set in the slot 53 across the end of the screw. The slot being parallel to the plunger, indicates when the plunger is alined with the channels.

Inward movement of the screw increases the resultant of depression of each of the springs, and the increase is greater in each of the springs 53 and 55 in proportion to their early depression than in the spring 48, while this ratio is greater in the third spring than in the second one. This adjustment varies the retardation and counter recoil in such manner as to control the rate of fire in conjunction with other functions of the arm, within the practicable range of the firing mechanisms of the as has heretofore been done with other b'u'fier devices. The adjustment also permits the adjustment of the phase relation of fire and counter re'c'oil so that smoothing of the vibrations of the gun may be improved. This is not possible with the 'oil bufier or with ordinary spring assemblies.

We have disclosed the invention in detail as the best form known to us at this time, but it will be understood that modifications in construction and arrangement, substitution of materials and substitution of equivalents, mechanical or otherwise may be made therein without departing from the spirit of the invention as 'more particularly set forth in the appended claims, where- We claim:

1. A buffer device for insertion in a gun action having a recoil member of the character described, comprising a tube having a spring seat at one end, a plunger fitted slidably therein, means on said plunger forming an annular external spring seat therearound at its outer end, a helical spring confined between the last named seat and the first spring seat, means on said tube and plunger to limit outward movement of the latter, a plug screw threaded in one end of said tube, said last mentioned means adapted to stop said plunger short or said plug, a helical spring in the tube between the said plug and plunger, means on the outer end of the plunger for connecting the same and the recoil member of the gun action, said plunger having a bore extending from the rear end of the plunger, a post on the plug adapted to slide in the plunger bore short of the forward end thereof, and a third compression spring in said bore.

2. The structure of claim 1, said second and third springs having uncompressed lengths such as to allow limited initial convergent movement of the plunger and screw seat without compression of these springs, the second spring being of such a length as to be compressed a distance before the third spring is loaded.

UNITED STATES PATENTS Name Date Gabbett-Fairfax Oct. 8, 1901 Lovelace May 18, 1909 Browning May 10, 1927 Bull et a1 Sept. 8, 1931 Anderson June 24, 1947 FOREIGN PATENTS Country Date Germany Dec, 20, 1910 

